Dust-Fiber Relationships In The Quebec Chrysotile Industry

Our plain-English summary of Dust-Fiber Relationships In The Quebec Chrysotile Industry, by G.W. Gibbs, M. Lachance (1974).

The study

• Authors: G.W. Gibbs, M. Lachance
• Published: Archives Of Environmental Health 28(2):69-71, February (1974)
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library, J-M no. 001267. The article is still under copyright, so we describe it here rather than post it.

In plain English

This study compared two ways of measuring airborne dust in the Quebec chrysotile mining and milling industry. Earlier health studies of these workers had used the midget impinger, which counts particles and fibers together, rather than membrane filters, which count fibers. In August 1971 and 1972, the authors took 87 side-by-side pairs of samples at up to nine sites in each of five mines and mills. Among 56 samples with more than 1 fiber per field, the methods correlated at 0.32, or 0.45 after logarithmic transformation. Among 31 samples with less than 1 fiber per field, the figures were -0.03 and 0.25. The best correlation improved prediction by only 13% over a conversion obtained at random. The ratio between the two counts differed between mines using the same process, and between production stages within the same mine and mill. The authors concluded that no single conversion factor applied. They concluded that, until satisfactory conversion factors are found, standards at least for mines and mills should rest on particle counts. They called the work a pilot investigation with only 87 pairs.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Preliminary (pilot) side-by-side comparison of two air-sampling methods. It was carried out because epidemiological studies of Quebec chrysotile miners and millers had related health to dust measured with the midget impinger.
• Who was studied: Up to nine selected work sites in each of five mines and mills of the Quebec chrysotile mining and milling industry, surveyed in August 1971 and 1972. In total, 87 pairs of samples were taken.
• Exposure: Airborne chrysotile dust measured two ways: midget impinger counts, which include both particles and fibers, and membrane filter counts, which count fibers only.
• Main results:
  • For the 56 samples with more than 1 fiber per field, the linear correlation between membrane filter and midget impinger counts was 0.32. After a logarithmic transformation of both measures it was 0.45.
  • For the 31 samples with less than 1 fiber per field, the linear correlation was -0.03, very close to zero. After logarithmic transformation it was 0.25.
  • Using the best correlation (0.45) to predict fiber counts from impinger counts was only 13% better than a conversion obtained at random.
  • By work area, the ratio of membrane filter to midget impinger counts in some mines was of a different order from that in other mines using the same process.
  • The ratios also varied with stage of production within the same mine and mill.
  • No single conversion factor could be applied to all mines or to all work areas within a mine.
• The authors' conclusion: The authors concluded that converting dust-disease relationships in the Quebec mining and milling industry into fiber-disease relationships did not seem possible at the time. Until satisfactory conversion factors are derived, they considered it best to base standards, at least for mines and mills, on particle counts.
• Limitations the authors state:
  • Only 87 pairs of samples were collected, in what the authors called a pilot investigation.
  • Fiber concentrations on the membrane filters were not always optimal. The authors attributed this to the low ratio of fiber to other particulates in some processes and to the sampling time limit set by evaporation of the impinger fluid.

Topics

Medical terms in this study, explained in our Lexicon: Quebec Chrysotile, Midget Impinger.

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